1. Field of the Invention
This invention relates to a heliostat used for a sunlight collecting system that utilizes sunlight as energy.
2. Prior Art
For the global environment, the CO.sub.2 problem is so serious that the present social system relying heavily on petroleum energy is a great concern for every country. In this context, as clean energy not affecting the environment, solar energy has attracted much attention. Particularly in countries in desert areas, projects for collecting solar energy to obtain huge energy have proceeded.
Those projects, however, have not gotten good results in performance and costs. The reason is that in order to utilize sunlight as energy, it is required to concentrate sunlight into a point to convert it into thermal energy and then to convert the thermal energy into electricity, in which there is difficulty in controlling heliostats for concentrating the sunlight into the point. The heliostats are arranged in large numbers around a light-collecting point for collecting the sunlight, and their individual concave mirrors are each rotated in both azimuth and altitude directions to reflect and converge the sunlight into the point. Since the above projects have attempted controlling the concave mirror of each heliostat by computer, the controlling is complex and difficult. More specifically, the movement of the sun changes in both azimuth and altitude with time, which fact causes difficulty in controlling the concave mirrors of the heliostats in large numbers simultaneously, pursuing the movement of the sun. Moreover, since the concave mirror of the heliostat has a diameter as large as ten-odd meters, the concave mirror can deform largely in such an area as a desert where the difference in temperature between day and night is large. As a result, the precision of information on a position sent from the concave mirror to the computer is likely to be lowered, which fact also causes difficulty in computer controlling.
The present invention directs its attention to the above prior art technique and provides a heliostat for a sunlight collecting system, a convex mirror of which can be controlled without computer.